Something I've noticed a lot on the Internet is the disparaging remarks 'net-lists' get and specifically anyone who uses them is just being a douche-bag who wants to win no matter what. Whilst this of course is the crux of the ridiculus "how you should have fun" argument, something which is often lost is what the real purpose of most net-lists are and that's the optimisation of a list concept. This is where spamming and "how you should have fun" comes into things with lists such as RazorMarines, triple Fire Dragons/Long Fangs/Dreadnoughts/Ravagers/etc, Venom Spam, Immolator Spam, etc. etc. come into play. These lists are designed, generally, to be the most mathematically potent lists. This means, in theory, the list is good and it's maximised for potential on the tabletop to be able to give the controlling player the best chance at winning games against equally skilled opponents with good army lists.
This assumes you can use the list to your best ability and whilst many players of great skill can use any list well (with little to no practice), you'll often see them running lists similar to what is defined as a net-list but which is clearly and distinctly different.
This is part of the reason net-list theory has often never translated to tournament wins (or certainly not the amount of wins it should have) - we never see the exact copy of net-lists running around on winning tournaments. Why? Because every person is a unique individual and they have their own preferences and play-styles and will end up putting their own tweaks on lists to suit them better. This is very different from arguing units like Legion of the Damned are just misundestood and not being used right but rather taking a concept and giving it a personal flare. It may dumb down the list a certain amount in relation to raw mathematical or potential output but it often fits the individual better which will lead to better and more consistent results.
Importantly though, the player is going to be happier using this list. Even just a few tweaks can make a list more personalised and fit the individual's style better. Again, the better players can generally pick up any army and do well but if they want to perform at their best, they need to have a good list concept which is moulded to their personal preferences. This could be as extreme as running a Footdar list (though in this case, one would often handicap themselves in terms of list power against other top players) or as tiny as running five Troops instead of six and putting things like Dozer Blades/HKMs on the rest of the army.
As the quote up top by SirBiscuit expounds, generalship informs list building. You can of course take a net-list just like it has been posted anywhere (or have an army built for you by someone) and run with it and after a lot of games, you'll become quite proficient and know the ins and outs of the list but the learning curve is going to be very different if you take that list and then modify it to how you like to run things. This is also part and parcel of identifying lists you would be comfortable with. For example, my favorite type of lists are mobile shooting forces which can either confuddle the enemy by running rings around them or move in and finish the opponent off. There's a reason I like BA, DE, Eldar and Tau and GK are what I always wanted my Space Marines to be (midfield shooting with counter-attacking options). I still play and enjoy other armies (come on Vince, get that Necron stuff going =D!) but the armies I collect are a combination of asthetic appeal and what fits with how I want to play.
I can still use lists outside of this concept and often do to ensure my understanding of such lists remains high but in terms of collecting and taking to tournaments - I'm going to go with what I'm comfortable with and that generally means taking an optimised concept and tweaking it more to my personal taste. This doesn't change the list so drastically the concept has changed but rather morphs it to keep that concept in mind whilst allowing me to be more comfortable using it. These are the type of combinations we see doing well consistently and whilst part of the list may look strange to an outsider or like a de-optimisation from a 'mathematically perfect forumla', the list isn't everything.
Remember this and know yourself and you'll do fine ^^ (and this goes for any gaming system really).
